The present invention relates to a method and apparatus for decorating ceramic and glass flat plates and to a toner powder use in such a system. Flat plates or substrates of this kind are processed in an apparatus in which the substrates are moved from one processing station to another and are provided with a print in each of the processing stations. In conventional processing stations for decorating ceramic and glass substrates, use is made, for example, of a screen printing apparatus. For this purpose, a screen has to be made for each series of substrates in order to print the same. In the case of multi-color printing, more of these screens are required.
Making the required screens in this way is extremely complicated and expensive and obstructs rapid change of substrates with different prints. The processing machines have to be stopped for each new image in order to replace the screens and re-start the process.
The decoration of ceramic and glass substrates can also be carried out in accordance with EPT 0 647 885, wherein an electrophotographic method is used to make an intermediate original, e.g. a paper substrate covered with gum Arabic, the intermediate original subsequently being brought into contact with the substrate. The toner image applied to the intermediate original is then transferred to the ceramic or glass substrate in a manner similar to the decalcomania process. The transferred image is then fired into the substrate at high temperature. This method requires considerable manual labor and is time-consuming. The object of the present invention is to drastically reduce the above disadvantages.
To this end, according to the present invention, use is made of a method and apparatus for printing ceramic or glass substrates, wherein a fusible powder is applied to an image forming medium in order to form an image and transferred to an intermediate medium, the powder image on the intermediate medium being brought into contact with the ceramic or glass substrate in a contact zone, the substrate being heated in a preheating device before the contact zone to a temperature of at least 60.degree. C., e.g. 60.degree. to 100.degree. C. and wherein the intermediate medium in the contact zone is heated to a temperature of at least 100.degree. C., e.g. 100.degree. to 140.degree. C. As a result, different images can be applied to the image forming medium in rapid succession and these images can be transferred to the ceramic or glass substrates without stopping the processing machine, thus increasing the machine productivity and providing bonding between the transferred images and the substrates. High quality mechanically resistant decorations are obtained if the image is fired in the ceramic or glass substrate.